1. Field of the Invention
The present invention relates to fiber optic signal amplifiers and thermoelectric generators. More particularly, the present invention relates to a remote amplifier for optical fibers transmitting light signals that is powered by a thermoelectric generator.
2. Discussion of Background
In current optical fiber communication systems, optical amplifiers or amplifier/repeaters are included in transmission lines at periodic intervals to compensate for attenuation of the light signal. Currently, the most successful kind of optical amplifier involves pumping light with an optical fiber doped with a rare-earth element, such as erbium.
Erbium-doped amplifiers are made by doping a segment of the fiber with erbium and then exciting the erbium atoms to a high energy level through the introduction of pumping light. The energy is transferred gradually to signal light passing through the fiber segment during excitation, resulting in an amplification of the signal light upon exit from the amplifier.
Erbium-doped amplifiers are known for use with optical fibers. U.S. Pat. Nos. 5,136,420, issued to Inagaki et al, and 5,140,456, issued to Huber, both disclose erbium-doped amplifier for use with optical fibers. Inagaki et al (U.S. Pat. No. 5,136,420) disclose reflective films and fiber loops that allow the amplifier to utilize pumping light more efficiently. Huber discloses an amplifier whereby pumping light has two wavelengths, one for low noise and the other for high power efficiency.
Also of interest and relating to optical fiber amplifiers are the apparatus described in U.S. Patents issued to Heidemann (U.S. Pat. No. 5,170,447) and Grasso et al (U.S. Pat. No. 5,054,876). Heidemann discloses coupling and transmission of more than one light signal and Grass et al disclose an optical fiber amplifier with reduced noise.
Like optical fiber amplifiers, thermoelectric generators are known in the prior art. In general, thermoelectric generation involves a heat source applied to a thermoelectric converter, which is typically two dissimilar materials with different thermal conductivities. With the addition of a heat sink, a thermal gradient is established across the two materials, causing an electric potential difference to be established across the two materials.
Several U.S. Patents disclose various aspects of thermoelectric generators. For instance, in U.S. Pat. No. 4,020,368, Carney describes a thermoelectric generator using a nuclear heat source in combination with a thermoelectric converter. Also, U.S. Pat. No. 3,840,431, issued to Devin et al, discloses a submarine nuclear reactor and the use of thermionic diodes to convert the nuclear energy to electrical power.
Other relevant U.S. Patents include U.S. Pat. No. 3,663,306, in which Des Champs et al disclose a housing for radioisotopic thermoelectric generators capable of withstanding high external pressures (such as at great depths in the ocean). Also, in U.S. Pat. No. 3,615,869, Barker et al disclose an assembly having improved remote replacement accessibility.